The transport of vital fluids in the human body is largely regulated by valves. Physiological valves are designed to prevent the backflow of bodily fluids, such as blood, lymph, urine, bile, etc., thereby keeping the body's fluid dynamics unidirectional for proper homeostasis. For example, venous valves maintain the upward flow of blood, particularly from the lower extremities, back toward the heart, while lymphatic valves prevent the backflow of lymph within the lymph vessels, particularly those of the limbs.
Because of their common function, valves share certain anatomical features despite variations in relative size. The cardiac valves are among the largest valves in the body with diameters that may exceed 30 mm, while valves of the smaller veins may have diameters no larger than a fraction of a millimeter. Regardless of their size, however, many physiological valves are situated in specialized anatomical structures known as sinuses. Valve sinuses can be described as dilations or bulges in the vessel wall that houses the valve. The geometry of the sinus has a function in the operation and fluid dynamics of the valve. One function is to guide fluid flow so as to create eddy currents that prevent the valve leaflets from adhering to the wall of the vessel at the peak of flow velocity, such as during systole. Another function of the sinus geometry is to generate currents that facilitate the precise closing of the leaflets at the beginning of backflow pressure. The sinus geometry is also important in reducing the stress exerted by differential fluid flow pressure on the valve leaflets or cusps as they open and close.
Thus, for example, the eddy currents occurring within the sinuses of Valsalva in the natural aortic root have been shown to be important in creating smooth, gradual and gentle closure of the aortic valve at the end of systole. Blood is permitted to travel along the curved contour of the sinus and onto the valve leaflets to effect their closure, thereby reducing the pressure that would otherwise be exerted by direct fluid flow onto the valve leaflets. The sinuses of Valsalva also contain the coronary ostia, which are outflow openings of the arteries that feed the heart muscle. When valve sinuses contain such outflow openings, they serve the additional purpose of providing blood flow to such vessels throughout the cardiac cycle.
When valves exhibit abnormal anatomy and function as a result of valve disease or injury, the unidirectional flow of the physiological fluid they are designed to regulate is disrupted, resulting in increased hydrostatic pressure. For example, venous valvular dysfunction leads to blood flowing back and pooling in the lower legs, resulting in pain, swelling and edema, changes in skin color, and skin ulcerations that can be extremely difficult to treat. Lymphatic valve insufficiency can result in lymphedema with tissue fibrosis and gross distention of the affected body part. Cardiac valvular disease may lead to pulmonary hypertension and edema, atrial fibrillation, and right heart failure in the case of mitral and tricuspid valve stenosis; or pulmonary congestion, left ventricular contractile impairment and congestive heart failure in the case of mitral regurgitation and aortic stenosis. Regardless of their etiology, all valvular diseases result in either stenosis, in which the valve does not open properly, impeding fluid flow across it and causing a rise in fluid pressure, or insufficiency/regurgitation, in which the valve does not close properly and the fluid leaks back across the valve, creating backflow. Some valves are afflicted with both stenosis and insufficiency, in which case the valve neither opens fully nor closes completely.
Because of the potential severity of the clinical consequences of valve disease, valve replacement surgery is becoming a widely used medical procedure, described and illustrated in numerous books and articles. When replacement of a valve is necessary, the diseased or abnormal valve is typically cut out and replaced with either a mechanical or tissue valve. A conventional heart valve replacement surgery involves accessing the heart in a patient's thoracic cavity through a longitudinal incision in the chest. For example, a median sternotomy requires cutting through the sternum and forcing the two opposite halves of the rib cage to be spread apart, allowing access to the thoracic cavity and the heart within. The patient is then placed on cardiopulmonary bypass, which involves stopping the heart to permit access to the internal chambers. Such open heart surgery is particularly invasive and involves a lengthy and difficult recovery period. Reducing or eliminating the time a patient spends in surgery is thus a goal of foremost clinical priority.
One strategy for reducing the time spent in surgery is to eliminate or reduce the need for suturing a replacement valve into position. Toward this end, valve assemblies that allow implantation with minimal or no sutures would be greatly advantageous. Attaching a valve such as a tissue valve to a support structure such as a stent may enable a valve assembly that allows implantation with minimal or no sutures. It is important that such valve constructs are configured such that the tissue leaflets or the support valve don't come into contact with the support structure, either during the collapsed or expanded state, or both in order to prevent abrasion. Such contact is capable of contributing undesired stress on the valve leaflet. Moreover, it is advantageous that such support structures are configured to properly support a tissue valve having a scalloped inflow annulus such as that disclosed in the U.S. patent application Ser. No. 09/772,526, issued as U.S. Pat. No. 6,682,559 on Jan. 27, 2004, which is incorporated by reference herein in its entirety.
Accordingly, there is a need for a valve replacement system comprising a collapsible and expandable valve assembly that is capable of being secured into position with minimal or no suturing; facilitating an anatomically optimal position of the valve; maintaining an open pathway for other vessel openings of vessels that may be located in the valvular sinuses; and minimizing or reducing stress to the tissue valve leaflets. The valves of the present invention may comprise a plurality of joined leaflets with a corresponding number of commissural tabs. Generally, however, the desired valve will contain two to four leaflets and commissural tabs. Examples of other suitable valves are disclosed in U.S. patent application Ser. No. 09/772,526, issued as U.S. Pat. No. 6,682,559 on Jan. 27, 2004, Ser. No. 09/853,463, issued as U.S. Pat. No. 6,682,558 on Jan. 27, 2004, Ser. No. 09/924,970, issued as U.S. Pat. No. 6,673,109 on Jan. 6, 2004, Ser. No. 10/121,208, issued as U.S. Pat. No. 6,719,787 on Apr. 13, 2004, Ser. No. 10/122,035, issued as U.S. Pat. No. 6,736,846 on May 18, 2004, Ser. No. 10/153,286, issued as U.S. Pat. No. 6,719,789 on Apr. 13, 2004, and Ser. No. 10/153,290, issued as U.S. Pat. No. 6,718,788 on Apr. 13, 2004, the disclosures of all of which are incorporated by reference in their entirety herein. Likewise, the systems and methods disclosed in U.S. patent application Ser. No. 10/831,770, filed Apr. 23, 2004 which published as US2005/0240200 on Oct. 27, 2005, are fully incorporated by reference herein.
As mentioned above, an open-heart valve replacement is a long tedious procedure. For implantation of a bioprosthetic valve in the aortic position, a surgeon typically opens the aorta and excises the native valve. The surgeon then inserts the prosthetic valve through the opening in the aortic wall and secures the prosthesis at the junction of the aorta and the left ventricle. The inflow annulus of the valve faces the left ventricle and, relative to the surgeon's perspective, may be termed the distal annulus, while the outflow annulus of the valve faces the aorta and may be termed the proximal annulus.
An alternative procedure for approaching the left atrium and the aortic or mitral valve is by intravascular catherization from a femoral vein through the cardiac septum, which separates the right atrium and the left atrium. Yet another alternative for approaching the left atrium and the aortic or mitral valve is by intravascular catherization from a femoral artery up through aortic valve.
Andersen et al. in U.S. Pat. No. 6,582,462, entire contents of which are incorporated herein by reference, discloses a valve prosthesis for implantation in a body channel having an inner wall, the prosthesis comprising a radially collapsible and expandable cylindrical stent, the stent including a cylindrical support means having a cylinder surface; and a collapsible and expandable valve having commissural points, the valve mounted to the stent at the commissural points, wherein the stent and valve are configured to be implanted in the body by way of catheterization. It is one aspect of the present invention to utilize a balloon expandable stent coupled with a tissue valve. An alternative embodiment in the present invention to utilizing a balloon expandable stent is to utilize a self-expandable stent. Yet another alternative embodiment of the present invention to utilizing a balloon expandable stent is to utilize a stent that may be expanded with mechanical means.
Sterman et al. in U.S. Pat. No. 6,283,127, entire contents of which are incorporated herein by reference, discloses a device system and methods facilitating intervention within the heart or great vessels without the need for a median sternotomy or other form of gross thoracotomy, substantially reducing trauma, risk of complication, recovery time, and pain for the patient. Using the device systems and methods of the invention, surgical procedures may be performed through percutaneous penetrations within intercostal spaces of the patient's rib cage, without cutting, removing, or significantly displacing any of the patient's ribs or sternum. The device systems and methods are particularly well adapted for heart valve repair and replacement, facilitating visualization within the patient's thoracic cavity, repair or removal of the patient's natural valve, and, if necessary, attachment of a replacement valve in the natural valve position.
Haluck in U.S. Pat. No. 6,685,724, entire contents of which are incorporated herein by reference, discloses a surgical instrument for use in performing endoscopic procedures having a handle and an elongate tubular member having a proximal end coupled with the handle for being disposed externally of the anatomical cavity and a distal end for being disposed within the anatomical cavity. The distal end further includes a pair of opposed, relatively movable jaws that form a grasping portion operable by manipulation of the handle to releasably grasp a releasable trocar. The releasable trocar has a complementarily shaped shank, a relatively sharp tip and may include a pair of blunt-edge tissue separators that project outwardly from the outer surface of the trocar.
Endoscopic and minimally invasive medical procedures, such as laparoscopy, have become widely accepted for surgery and illness diagnosis. This is due to reduced trauma to the patient and reduced hospitalization time. Other techniques exist for creating a working space within the body cavity. At the beginning of most laparoscopic cases, a small incision is made, followed by a small (about 1 cm) port in the remaining layers of the tissue wall so as to gain access to the cavity.
Hunsberger in U.S. Pat. No. 6,613,063, entire contents of which are incorporated herein by reference, discloses a trocar assembly which includes a shank having a distal end and a proximal end, and a planar piercing blade having two substantially flat faces and a cutting contour, where the piercing blade is integrally attached to the distal end of the shank. The shank tapers inwardly towards the opposed flat faces of the piercing blade.
Further, McFarlane in U.S. Pat. No. 6,478,806, entire contents of which are incorporated herein by reference, discloses a tissue penetrating instrument of the type used in the medical field and which may or may not be embodied in the form of an obturator associated with a trocar assembly, wherein the instrument includes an elongated shaft having a penetrating tip mounted on one end thereof. The penetrating tip includes a base secured to the one end of the shaft and a distal extremity spaced longitudinally outward from the base and formed into an apex which may be defined by a point or other configuration specifically structured to facilitate penetration or puncturing of bodily tissue.
Spenser et al. disclose in U.S. patent application Ser. No. 09/975,750, issued as U.S. Pat. No. 6,893,460 on May 17, 2005, Ser. No. 10/270,252, issued as U.S. Pat. No. 6,730,118 on May 4, 2004, and Ser. No. 10/637,882, which published as US2004-0039436 on Feb. 26, 2004, the entire contents of which are incorporated herein by reference, disclose and implantable prosthetic valve that comprises a support sent to be initially crimped in a narrow configuration suitable for catherization through the body duct to a target location.
Key features of any valve where sutures to hold the replacement valve into position are to be eliminated or reduced are: durability, low-pressure gradient across the valve, sufficient seal around the valve to prevent perivalvular leak, and prevent migration. Therefore, it would be desirable to provide an implantable valve that with features that aim to increase durability, reduce pressure gradient across the valve, and provide an adequate seal around the valve and prevent migration.